UST892005I4

ABSTRACT

WET-PROCESS ACID AND MIXTURES OF WET-PROCESS ACID AND ELECTRIC-FURNACE ACID ARE CLARIFIED BY HEATING TO PREDETERMINED TEMPERATURES AND ADDING AMMONIUM NITRATE TO SAID HOT ACIDS. THE MINIMUM TEMPERATURE IS DICTATED BY (1) ABSOLUTE MINIMUM TEMPERATURE AT WHICH THE OXIDIZING TEMPERATURE TO WHICH THE PRODUCT WILL BE RAISED IN SUBSEQUENT PROCESSING. THE AMMONIUM NITRATE ACTS AS AN OXIDIZING AGENT UPON PARTIALLY DECOMPOSED ORGANIC MATERIALS PRESENT IN WET-PROCESS ACIDS PRODUCED FROM UNCALCINED ORES, AMMONIUM NITRATE IS ADDED SUBSEQUENT TO HEATING (1) TO PRECLUDE LOSS OF OXIDIZING POWER PRIOR TO REACHING THE TEMPERATURE AT WHICH IT WILL BE EFFECTIVE, AND (2) TO EFFECTIVELY MINIMIZE UNDERSIRABLE FOAM PRODUCTION AND ACCUMULATION. FROM 0.1 TO 2 PERCENT AMMONIUM NITRATE IS NEEDED DEPENDING ON THE PROPORTION OF WET-PROCESS ACID MIXED WITH ELECTRIC-FURNACE ACID AND THE CONCENTRATION OF THE ACID. THE MINIMUM TEMPERATURE FOR REMOVAL OF THE BLACK MATERIAL IS ABOUT 250*F. AND THE UPPER RANGE IN FINAL PROCESSING TO FERTILIZERS IS ABOUT 400*F. IF THE ACID IS SUBSEQUENTLY RAISED TO A TEMPERATURE HIGHER THAN THAT AT WHICH THE AMMONIUM NITRATE WAS INITIALLY ADDED, FURTHER DECOMPOSITION OF DISSOLVED ORGANIC MATERIAL CAUSES RETURN OF THE BLACK COLOR.



